(53) باب فِي الْحَوْضِ
Narrated Ibn `Abbas:
The word 'Al-Kauthar' means the abundant good which Allah gave to him (the Prophet (ﷺ) Muhammad). Abu Bishr said: I said to Sa`id, "Some people claim that it (Al-Kauthar) is a river in Paradise." Sa`id replied, "The river which is in Paradise is one item of that good which Allah has bestowed upon him (Muhammad).
Reference: Sahih al-Bukhari 6578
In-book reference: Book 81, Hadith 166
USC-MSA web (English) reference(deprecated numbering scheme): Vol. 8, Book 76, Hadith 580